1. Field of the Invention
This invention relates to a tolane compound which is useful as an electrooptical display material More particularly, it relates to an alkynyloxy or alkadienyloxytolane compound which is useful in elevating the anisotropy of the refractive index of an STN liquid crystal material when mixed with said liquid crystal material.
2. Description of the Prior Art
Recent development of STN liquid crystal cells shows a tendency toward black-and-white or full-colored ones, apart from conventional green or blue modes. Furthermore, it has been simultaneously attempted to develop a liquid crystal cell of high-speed response so as to satisfy the demand for animated images It is expected that the response rate of a STN liquid crystal cell can be elevated by reducing the thickness of the liquid crystal cell layer. In this case, however, the liquid crystal material to be charged into the cell should have a high anisotropy (.DELTA.n) of the refractive index. Although some tolane compounds having a relatively high .DELTA.n have been proposed therefor, none of them has a sufficiently high .DELTA.n. Thus it has been urgently required to develop a tolane compound having a higher .DELTA.n.